1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a bistable liquid crystal display.
2. Description of the Related Art
Bistable liquid crystal displays have received considerable attention recently because they can operate at lower power levels at their two stable states without the application of any electric field.
Among the bistable devices, the bistable twisted nematic liquid crystal cell can be switched between the (ψ−π) and (ψ+π) twisted states by controlling the flow effect. However, the durations for the liquid crystal maintaining these two states are not very long. Indeed, the intermediate ψ state is more stable. Although a long-term bistability has been achieved by using multidimensional alignment structure to prevent the liquid crystal of the ψ state from nucleation, the application is still limited. To make the states of the liquid crystal truly stable, the π-BTN liquid crystal cells including BiNem, COP-BTN and SCBN-LC, which also use flow effect to switch between ψ state and (ψ+π) state, are demonstrated one after another. However, the BiNem and COP-BTN liquid crystal cells need asymmetric anchoring energy substrates in order to achieve anchoring energy breaking and the SCBN-LC and COP-BTN liquid crystal cells need three-terminal electrode structure to produce the horizontal and vertical fields to switch states. The manufacture processes of these special substrates are not only difficult to be controlled but also difficult to match the standards for LC display. There are also other designs of the bistable display such as the ZBD (Zenithal Bistable Display) and the micro-patterned surface alignment device that have very long-term bistability. However the substrates of the ZBD which have the microstructure relief grating with short pitch and deep profile, and the micro-patterned surface alignment device which use the atomic force microscope (AFM) nano-rubbing technique to have orientational patterns are even more delicate and not easy to be manufactured.
In view of the above reasons, there exists a need for a bistable liquid crystal display which overcomes the above-mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.